Wrong shadows with Cycles Renderer
Incomplete node setup

Normal maps need a conversion  before you feed them to the shaders. The black spots you are experiencing are not shadows, but an incorrect calculation of the surfaces normals.

A Normal Map node must be added between the texture and the shader.

As said in the manual:


  The Normal Map node generates a perturbed normal from an RGB normal
  map image. This is usually chained with an Image Texture node in the
  color input, to specify the normal map image.